mid ocean ridge - longest chain of mountains
sonar - records objects with sound waves
sea floor spreading - process that adds new material to ocean floor
deep ocean trenches - deep water canyons
subduction - when ocean floor sinks beneath a deep ocean trench

Evidence for sea floor spreading

• evidence from molten material
  • toothpaste shape rocks
  • must have erupted over and over
• Evidence from Magnetic stripes
  • reversals of magnetic fields
  • rocks lie in patterns of magnetic stripes
• evidence from drilling samples
  • farther away from ridge older; closer=younger

Subduction at deep ocean trenches